I don't have access to a lathe small enough to deal with this type of work so I was pretty much stuck finding something close and working with it.
From the dimensions I got over at DigitalCorvettes the tank is 5.5" by 20" or .220" by .8" in scale. After talking with Jim, one of the maintenance guys at work, he suggested an old #2 drill bit. We took some measurements and the shank of the bit came out at .219" and he donated an old dull one to me. Let me tell yeah working with high-speed tool steel was a lot of fun :roll: but here's the result:
This is the tank upside down but it measures .219" by .801" after I put the concave radius on the bottom. After looking back at my reference pics, the tank sits in the fenderwell at a slight angle (top towards the motor)and the top of the tank is not perfectly flat all across. Part of the top is level when installed at an angle in the car so I have to put a facet on the top of the tank. My next step will be to make a casting of the metal billet and work with the resin copy for the final shaping of the top of the tank since it is the most visible part of the whole gig. This metal is just too hard to work with and I don't want to go back down to work on my holiday weekend to use their equipment. When I get the top right, I'll add the flange that's about 1/3 of the way down from the top and make another casting of the finished tank in case I ever decide to build another one of these again.
After some eyeball engineering, I decided the full length tank can be duplicated on the model. I'll have to thin the firewall down to almost scale thickness and rework the inner fender a little. On the inner fender, I'm getting ready to attach a piece of .030" sheet stock on the suspension side of the kit inner fender, shape in the notches where it meets the frame and file out the original kit inner fender. This will leave just enough room for the tank to drop all the way down and attach to the frame like on the 1:1.
I really need to figure out why my camera does this purple tint thing in macro mode.
Sorry for the long post and thanks for looking.